An image pickup apparatus which divides an exit pupil of a photographing lens into a plurality of areas and can simultaneously photograph a plurality of parallax images corresponding to the divided pupil areas has been proposed.
PTL 1 discloses an image pickup apparatus having a two-dimensional image pickup element in which one pixel corresponds to one microlens and the pixel is formed by a plurality of divided photoelectric conversion units. The divided photoelectric conversion unit is constructed so as to receive light from different partial pupil areas of an exit pupil of a photographing lens through one microlens and performs a pupil division. A plurality of parallax images corresponding to the divided partial pupil areas can be formed from an image signal generated by photoelectrically converting object light received by each of the divided photoelectric conversion units. PTL 2 discloses such a technique that a picked-up image is generated by adding, on the pixel basis, all of image signals which are output from divided photoelectric conversion units.
A plurality of photographed parallax images are equivalent to Light Field (LF) data serving as space distribution of light intensity and angle distribution information. NPL 1 discloses such a refocus technique that by composing images on a virtual focusing plane different from an image pickup plane by using the obtained LF data, an in-focus position of the picked-up image is changed after the photographing.